A heat exchanger having fluid passages for a high temperature fluid to flow and fluid passages for a low temperature fluid to flow, the fluid passages being alternately disposed so that heat is exchanged between the high temperature fluid and the low temperature fluid, is already known from, for example, Japanese Utility Model Registration Application Laid-open No. 3-79082, Published Japanese Translation No. 5-506918 of a PCT Application, and U.S. Pat. No. 3,831,374.
In the Japanese Utility Model Registration Application Laid-open No. 3-79082, a large number of gap-maintaining parts are projectingly provided by bending paper partitions at predetermined intervals, the gap-maintaining parts extending parallel to each other, and a plurality of the partitions are alternately superimposed on each other so that the gap-maintaining parts are perpendicular to each other, thus alternately forming fluid passages for a high temperature fluid to flow and fluid passages for a low temperature fluid to flow between adjacent partitions.
The Published Japanese Translation No. 5-506918 of a PCT Application discloses an annular heat exchanger used for a gas turbine engine, in which a large number of involutely curved heat transfer plates are disposed at predetermined intervals between coaxially disposed outer and inner casings, thus alternately forming in the circumferential direction high pressure fluid passages for compressed air to pass and low pressure fluid passages for a combustion gas to pass.
Furthermore, the U.S. Pat. No. 3,831,374 discloses an annular heat exchanger used for a gas turbine engine, in which a large number of heat transfer plates are radially disposed at predetermined intervals between coaxially disposed outer and inner casings, thus alternately forming in the circumferential direction high pressure fluid passages for compressed air to pass and low pressure fluid passages for a combustion gas to pass. The low pressure fluid passages, through which the combustion gas passes from the front to the rear, extend linearly in the axial direction, whereas the high pressure fluid passages, through which the compressed air passes, include a compressed air inlet in a rear part of the outer casing and a compressed air outlet in a front part of the inner casing. The compressed air therefore flows in radially inward via the compressed air inlet, flows axially forward, and flows out radially inward via the compressed air outlet, and the high pressure fluid passages are thus formed in an overall crank shape.
In the arrangement disclosed in the U.S. Pat. No. 3,831,374, compressed air that has flowed from the front to the rear on the outer periphery of the heat exchanger turns radially inward through 90°, flows to the interior of the heat exchanger via the compressed air inlet, further turns toward the front through 90°, and flows toward the front through the high pressure fluid passages within the heat exchanger. Since the compressed air is forced toward the outside of the turn due to the centrifugal force caused by turning through 180°, it is difficult to make the compressed air, after it has turned, flow uniformly in the axially formed high pressure fluid passages within the heat exchanger, and there is a possibility that the heat exchange efficiency might deteriorate.
Furthermore, in a heat exchanger in which low pressure fluid passages and high pressure fluid passages are formed alternately between a large number of heat transfer plates stacked at predetermined intervals, a difference in pressure between a high pressure fluid flowing though the high pressure fluid passages and a low-pressure fluid flowing though the low pressure fluid passages generates a load to push the heat transfer plates toward the low pressure fluid passages, and there is a possibility that deformation will be caused between the heat transfer plates unless a large number of ridges for supporting the load are formed within the low-pressure fluid. On the other hand, it is not particularly necessary to form a ridge for supporting a load within the high pressure fluid passages, and it is sufficient for there to be a spacer-like ridge for maintaining a predetermined width in the high pressure fluid passages.